ENGINEERS are working out how to urgently repair the Tarro Rail Bridge but travellers have been warned the closures could be in place for weeks.
Traffic has been heavy on the stretch of the New England Highway and significant delays have been reported.
Authorities have now asked regular users of the road to try public transport, working from home or staggering work hours outside peak times if possible.
Major roads in and out of Newcastle have had an increase in traffic as people look for alternate travel routes to avoid the congestion chaos on the New England Highway at Tarro.
The two outer lanes of Tarro Rail Bridge were urgently closed last week after inspections turned up a critical safety issue.
A problem was first found during a routine inspection in July and a speed limit of 60 kilometres per hour was enforced, which remains in place.
"The defect relates to a structural issue with the columns supporting the outer lanes," a Transport for NSW spokesperson said.
"All site investigations are complete and our engineering teams are now assessing repair options.
"It is too early to determine how long it will take or how much repairs will cost, but the safety of the community is our key priority."
Specialist engineers have developed an initial report and are working with the Australian Rail Track Corporation.
The line is busy for both passengers and freight, but rail services aren't affected. The pedestrian and cycle way also remains open.
The Transport for NSW spokesperson said it was hard to estimate how long the urgent repairs would take or how much they will cost, but motorists should be prepared for the lanes to be closed for at least two weeks.
The authority thanked road users for their patience after the "unexpected and urgent" step was taken to close the two lanes on the bridge, one in each direction.
The closure came on the last weekend of the school holidays, causing significant delays for those returning to Newcastle from the coast.
